1. Field of the Invention
The present invention relates to method and apparatus for removing deposits to be applicable widely in industries in which it is necessary to remove dusts or other deposits from powdered or granular materials such as tablets, remove foreign matter adhering on the surface of semiconductor products, or remove dusts or other deposits from other materials. The invention may be also applied as the method and apparatus for classifying by sifting powdered or granular materials.
2. Prior Art
Hitherto, as the method for sifting powdered or granular materials capable of removing deposits from materials, the Japanese Patent Publication Sho. 52-10538 is known. This publication discloses what is shown in FIG. 10, which is designed to sift powdered or granular materials by using pulsating air.
The constitution in FIG. 10 is explained below. An exhaust port 501 and a takeout port 502 are provided in upper and lower parts of a hopper-shaped casing 500, and a sieve mesh 503 is stretched horizontally in the casing 500, and pulsating air or non-pulsating air flow is sent to a material layer 504 above the sieve mesh 503 from an air pipe 505 opened downward of the sieve mesh 503 to fluidize the powdered or granular materials on the sieve mesh 503, so that the materials of specified particle size may be sifted. That is, the takeout port 502 communicates with a proper exhaust device or separating device in next step, for example, cyclone device, and the air is sucked out in the direction of arrow a, and therefore the powdered or granular materials on the sieve mesh 503 are fluidized by the vertical reciprocal air flow continuously as indicated by arrow b as cooperating action with pulsating air by the air pipe 505.
In short, in this prior art, by the cooperating action of the air flow from the air pipe 505 toward the material layer 504 and the downward air flow from the takeout port 502, the pulsating waves (arrow b) reciprocating vertically on the material layer 504 above the sieve mesh 503 act to effect classifying action.
Therefore, in the prior art, in order to fluidize the material layer 504 on the sieve mesh 503 by the vertical reciprocal air flow b (plus and minus method), the air flow from the air pipe 505 must be actuated by a considerably large energy, and hence the noise increases. To suppress the noise, the casing 500 must be put in a case made of soundproof wall such as concrete. It hence requires a special soundproof case, and it is not practical.
The invention is devised in order to solve these problems, and presents a method capable of removing deposits from materials by applying air vibrations, and an apparatus for realizing such method.